1. Field of the Invention
This invention relates to an optical fiber end processing method and an optical fiber end processing apparatus, for processing an end of an optical fiber configured to have a plurality of air holes around a core, and relates to the optical fiber end.
2. Description of the Related Art
In recent years, a new optical fiber having a plurality of air holes around a core, which is called as “holey fiber” or “photonic crystal fiber”, has been noted, and its widespread applications to optical communication cords, optical devices, and the like have been studied (see, e.g., Hasegawa, “THE TREND OF DEVELOPMENT IN PHOTONIC CRYSTAL FIBERS AND HOLEY FIBERS,” monthly publication “OPTRONICS,” The Optronics Co., Ltd. No. 7, pp. 203-208 (2001)).
A typical holey fiber comprises a core, a cladding formed around a circumference of the core, and a plurality of air holes formed around the core in an axial direction of the core.
If the air holes formed in the cladding are open at an end face of the holey fiber, moisture may enter the air holes, or dew may form in the air holes due to temperature variations, leading to lowering in mechanical strength of the holey fiber, or variation in optical characteristics thereof.
Also, when the optical fibers are spliced together by use of a splicing member such as a mechanical splice, an MT connector, or the like, there is used a method to fill a gap between connected end faces of one of the optical fibers and the other thereof with a liquid material for refractive index matching, so as to reduce reflection and loss at the connected end faces. When this connecting method is applied to the holey fiber with the air holes being open at the end face of the holey fiber, the liquid refractive index matching material is likely to flow from the connected end faces into the air holes. This may cause the liquid refractive index matching material at the connected end faces to run out, leading to significant reflection and connection loss.
Also, in a single fiber optical connector requiring no refractive index matching material, there is a problem that when the end face of the holey fiber is ground (polished), an abrasive or grinding swarf thereof enters the air holes, thereafter comes out from the air holes and get stuck between the connected end faces in such a manner as to cause damage to the fiber end face, or an air gap therein, thereby degrading the optical characteristics of the holey fiber.
The following techniques to solve the above problems have been suggested.
JP-A-2004-4320 discloses a method of plugging openings of pores (air holes) in an end face of a photonic crystal fiber with a plugging material having a refractive index lower than a refractive index of a core.
JP-A-2002-323625 discloses a method of sealing hollow portions (air holes) of an optical fiber by heating an end face of the optical fiber to soften a cladding, thereby collapsing the hollow portions, or by filling the hollow portions with a resin to seal the hollow portions.
JP-A-2005-24849 discloses a method of fusion plugging air holes by arc discharge at a position distant from an end face of an optical fiber.
Refer to, e.g., JP-A-2004-4320, JP-A-2002-323625, JP-A-2005-24849, and Hasegawa, “THE TREND OF DEVELOPMENT IN PHOTONIC CRYSTAL FIBERS AND HOLEY FIBERS,” monthly publication “OPTRONICS,” The Optronics Co., Ltd. No. 7, pp. 203-208 (2001).